// 一像素边框
border-1px($color, $offset=bottom)
  &::before
    content ""
    position absolute
    width 100%
    height 1px
    background-color $color
    if $offset == top
      top 0
    else
      bottom 0

    @media screen and (-webkit-min-device-pixel-ratio: 2)
      transform scaleY(.5)
    @media screen and (-webkit-min-device-pixel-ratio: 3)
      transform scaleY(.33)




// 根据物理像素比 加载倍图 后缀
image-bg($url, $after_name)
  background url($url + $after_name)
  @media screen and (-webkit-min-device-pixel-ratio: 2)
    background url($url+ '@2x' + $after_name)
  @media screen and (-webkit-min-device-pixel-ratio: 3)
    background url($url+ '@3x' + $after_name)